CONCHIFERA. 



its muscular structure will be at once evident, and the disposition 

 of the several layers composing it more easily understood than 

 from the most elaborate verbal description. 



(416.) Diverse are the uses to which the foot may be turned. 

 It is generally used for burrowing in the sand or soft mud ; and, 

 by its constant and worm-like action, those species in which it is 

 largely developed can bury themselves with facility, and make 

 their way beneath the sand with a dexterity not a little remark- 

 able. Perhaps, the most efficient burro wers met with upon our 

 own shores are the Razor-shells (*$WewzW<z), in which family the 

 fleshy foot attains to enormous proportions ; and the rapidity of 

 their movements beneath the soil will be best appreciated by those 

 who may have watched the manner in which the fishermen effect 

 their capture. 



The Solen excavates for itself a very deep hole in the sand, bor- 

 ing its way by means of its foot to a depth of some feet ; and re- 

 mains concealed in this retreat, usually occupying a position within 

 a few inches from the surface. The fisherman, armed with a slen- 

 der iron rod, furnished with a barbed head, resembling a harpoon, 

 treads carefully backwards over the beach left bare by the retreat- 

 ing tide, and finds the holes in which Solen lodges, by watching 

 the little jet of water thrown out by the animal, when, being alarm- 

 ed by the shaking of the sand, it contracts its body. Guided by 

 the orifice through which the water is thrown, he plunges his rod 

 into the sand, and generally succeeds in piercing the animal with 

 the barbed extremity, and dragging it from its concealment ; but, 

 should he fail in his first attempt, he well knows that to try again 

 would be unavailing, for the animal instantly works its way down 

 to such a distance as to render pursuit hopeless. 



But, however efficient, as a means of burrowing, the foot may 

 be, it can be turned to other purposes. The Pholades, for, example, 

 by some means, either of a mechanical or chemical nature, not 

 as yet precisely determined, excavate the solid rocks, and form 

 therein chambers, in which they pass their lives. In such genera, 

 the foot, which would be useless as a boring instrument, by being 

 simply transformed into a broad and flat disc, becomes a powerful 

 sucker, whereby the Pholas fixes itself to the walls of its apart- 

 ment in any convenient situation. 



In many of the Cockle tribe we find the foot converted into 

 an instrument of locomotion, of a very singular description, en- 

 abling the cardiaceous Conchifera to leap by bounds we should 



